This application claims the priority of German Application No. 198 38 116.6, filed Aug. 21, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an electronically controlled ventilation system for a disk brake, particularly in the case of a vehicle.
A brake ventilation system is basically known for use with disk brakes. Because of the high contact pressure forces in the case of disk brakes, high temperatures may occur locally which have a disadvantageous effect on the braking performance. To avoid this effect, a ventilation system can be provided, particularly for highly stressed disk brakes. Usually, bores are arranged in the brake disks. The bores are designed such that a ventilator effect occurs during the rotation of the disk. As a result of this measure, lower temperatures are reached during braking and faster cooling is achieved after the braking operation. The bores can also be used for the rapid displacement of moisture during braking and for reducing weight.
However, it was found that a maximal ventilation is not always accompanied by an optimal braking effect.
It is therefore an object of the invention to provide a ventilation system for a disk brake which permits optimal braking in any driving condition and in case of any brake load.
This object is achieved in the case of a ventilated disk brake, by a device for changing the flow cross-section in the course of a flow duct leading to the disk brake. This device is acted upon by a control unit. As a function of input quantities, the control unit generates a ventilation signal corresponding to the desired change of the flow cross-section.
The object is also achieved by a method for controlling the ventilation of a disk brake wherein the cross-section of a flow duct in which course the disk brake is arranged is changed as a function of one or more input quantities or parameters.
By changing the flow cross-section in the flow duct extending to the brake disk, a cooling can be ensured which is adapted to the respective driving condition and to the respective brake load.
A simple embodiment is characterized in that a ventilation flap is provided as the device for changing the flow cross-section in the flow duct. The ventilation flap is driven by a motor, particularly a torque motor or a transmission motor. The ventilation flap exposes the flow duct in the open condition, closes it in the closed condition and, by means of a rotation, permits any intermediate position between the above-mentioned extreme open and closed positions. Of course, instead of the ventilation flap any other device for changing the cross-section of the flow chart can be chosen.
As already mentioned, the ventilation flap can be driven in a particularly simple manner by an electric motor which is acted upon by the control unit. According to a specific embodiment, it should be ensured that the flow duct is open in the event of a system failure. This has the result of cooling the brakes in a currentless condition. The foregoing can be achieved by a spring element which acts upon the ventilation flap in an open condition.
The brake lining thickness, the brake lining temperature and/or the wear condition of the brake disk can be taken into account as input parameters. As an alternative, other input parameters or quantities can also be taken into account. These parameters can be measured either directly or be calculated from quantities existing in the vehicle. In addition, the above-mentioned quantities can be placed on and taken from the CAN bus.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.